How water changes the landCopyright: Kella Randolph

How Water Changes the Land

• Also known as Fluvial Geomorphology• Fluvial is a term used in geography and geology to refer toThe processes associated with rivers and streams and the deposits and landforms created by them. Geo means EarthMorphology means the study of changes

K.K.E. Neuendorf, J.P. Mehl, Jr., and J.A. Jackson, eds., 2005, Glossary of Geology. American Geological Institute, Alexandria, Virginia. 800 pp.

Wear and Tear

Rivers both carve the land and build it up. As rivers flow, they cut into the land. This is called erosion. Rivers cut both down into and across the earth. As rivers cut into the earth, they grind up rocks and churn up small rocks and soil. Over time rivers change the land they flow over by carving new paths for themselves. All of the rocks, pebbles and soil that rivers churn up get carried downstream. As the river flows, it deposits all of the stuff it carries. Large items like rocks get deposited first. Soil is deposited last. Over time the soil that a river deposits can build up and create new land areas!http://www.nhptv.org/natureworks/nwep7j.htm

It’s all one big network

• From space, rivers and streams look like veins on the Earth's surface. Rivers and streams connect with each other in a system called a watershed.

• http://www.nhptv.org/natureworks/nwep7j.htm

There are three types of watersheds.

The rivers and streams in a closed watershed empty into an inland body of water like a lake. Open watersheds empty into the ocean from one source. Multiple open watersheds empty into the ocean from more than one source. Within watershed areas you will find other wetland areas like ponds, swamps and marshes.

Closed watershed

Open watershed

Multiple openwatersheds

Rivers

A river is freshwater flowing across the surface of the land, usually to the sea.

All rivers start at the highest point in an area. As the river flows downstream, it gains more water from other streams, rivers, springs, added rainfall, and other water sources.http://www.primaryhomeworkhelp.co.uk/rivers.htmlPhoto from Creative Commons

The source is where the river begins.

Some rivers begin where a natural spring releases water from underground.

Hot Springs, NC: Hot Springs, 2004 French Broad River http://www.city-data.com/picfilesc/picc6766.php

Every river has a 'source', a place where the river begins its journey.The source of a river is usually found in high places such as hills or mountains. A river can have more than one source.

Where do rivers begin? Lakes: The source of some rivers is a lake. The source of the River Nile is Lake Victoria, in Burundi.

http://members.virtualtourist.com/m/p/m/20e095/

Bogs: In some places, rain water can'tsink into the ground as the ground is too wet already. The water forms a bog.The water flows out of the bog to form lakes and streams. https://goingnccoastal.wordpress.com/coastcards/http://www.primaryhomeworkhelp.co.uk/rivers/source.html

Rainfall and melting snow:Some rivers begin in mountains or hills, where rain water or snowmelt collects and forms small channels

. At first, the channels are small and are called rills. As more water enters the channels they grow forming gullies (larger channels). The streams in the gullies eventually become big enough to form a river.

http://www.wallconvert.com/wallpapers/nature/mountain-stream-9601.html

Where do rivers end? At the mouth.

River deltas are land areas that are formed at the mouth or end of a river as the minerals and soil the river carries are deposited. Deltas are very rich in nutrients. Some of the best farmland on Earth can be found in river deltas.

Watershed

A watershed is the total area of land that drains into a particular waterbody (stream, wetland, river, lake or ocean). Land uses and runoff in a watershed determine the quality of surface water in smaller streams and waterways. They in turn influence the water quality of larger streams.

Humans and animals rely on rivers.

Most settlements were built along major rivers. Rivers provide us with food, energy, recreation, transportation routes, and of course water for irrigation and for drinking.

North Carolina River Basins and Watersheds

Many tributaries flow together to join larger bodies of water.

Top:www.bae.ncsu.edu

Right: the winding tributaries of the South Carolina low country

Right: gocharleston.com

. Watershed can be most simply defined as an area of land that drains water, sediment, and dissolved materials into a particular stream. A watershed or drainage basin boundary can be determined at any point along any stream or river by delineating the points of highest elevation in the surrounding land area that drains to the selected point on that stream. Watersheds can range in size from less than an acre to thousands of square miles. Each stream and its contributing watershed are part of an increasingly bigger drainage area. http://www.cityofws.org/portals/0/pdf/stormwater/Introduction_to_Watersheds_and_Streams_Section.pdf

North Carolina Watersheds

All watersheds have two things in common:

They collect and move precipitation from higher to lower elevations As the water washes over the land, it picks up pollutants such as oil, grease, fertilizers, pesticides, trash, and dirt. http://mysilvercreekwatershed.weebly.com/what-is-a-watershed.htmlhttp://www.carolana.com/NC/Transportation/nc_watersheds.html

Importance of Rivers

Although river water makes up only about 0.2 percent of all the fresh water on Earth, it plays a very important role. Rivers are like roads. They carry water, organisms and important gases and nutrients to many areas. They also help drain rainwater and provide habitats for many species of plants and animals. As they make their way to the sea, rivers help shape the features of the Earth. Rivers are travel routes for people and provide the power for hydroelectric plants.

River water makes up only about 0.2 percent of all the fresh water in the world, but it plays a very important role.http://www.nhptv.org/natureworks/nwep7j.htm

The Fluvial Cycle• These are the stages in the development and life of a river and its surrounding landscape. We note

that as a stream erodes closer and closer to base level, its velocity begins to slow down and erosion gives way to deposition. There are specific features associated with different cycles of stream erosion.

• Youth (youthful): steep irregular gradient, V-shaped valley from downcutting into bedrock, potholes, rapids, waterfalls, bed load, river far above base level

• Maturity: gentle gradient, floodplain begins, river starts to meander, creation of oxbow lakes, river nearing base level

• Old Age: very gentle gradient, wide floodplain with expansive meanders and oxbow lakes, oxbow swamps, meander scars. In particular, old age streams have natural levees built by floods. The levee is a sand bar deposit that runs parallel to river channel. Yazoo tributaries can also be found confined to the floodplain by the natural levees. River at base level or very close to it.

• Rejuvenated: was graded, but downcutting was reactivated by uplift which raises the river above base level. These streams are either mature or old age that have been made young again. The stream returns to a steep gradient with rapids and a "V" shaped valley. However, it still retains evidence of its past - it has meanders.

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Age of the meandering river Young: The river has only one main channel.Mature: Channel meanders from side to side in the floodplain. Example: Mississippi River and other rivers in the eastern U.S. Old Age: Meandering channels occur where bulk of stream load is fine and carried in suspension. Rejuvenated: Energetic streams with no bed load to down-cut. They achieve equilibrium by lateral planation. Meandering streams are not stable, the channel moves sideways across the floodplain at rates of 100s of meters per year.

Meandering Stream continued

When a meander becomes too extreme, erosion will carve through the narrow neck of land and the river will establish a straighter flow The old channel (after being cut-off) contains a crescent-shaped lake, called an oxbow lake. This lake can begin to fill with sediment and become an oxbow swamp and eventually completely fills in to leave a meander scar. See the illustration below that shows how the oxbow lake --> meander scar progression takes place.Example of typical features of a meandering river. At left center is an oxbow lake formed by cutoff and abandonment of a meander bend. Point bars occur on insides of meander bends. At right, continued cutbank erosion due to channel meandering is about to lead to a neck cutoff and abandonment of a meander loop. Flow direction is right to left. Width of view in bottom foreground is about 1 km. Wood River, south of Fairbanks, Alaska. Image Courtesy United States Geological Survey; Image source: Earth Science World Image Bank http://www.earthscienceworld.org/images Copyright © Society for Sedimentary Geology

Fluvial processes

Fluvial processes include the motion of sediment and erosion or deposition on the river bed .Erosion by moving water can happen in two ways. Firstly, the movement of water across the bed exerts a shear stress (scraping motion) directly onto the bed. If the cohesive (holding together) strength of the substrate is lower than the shear exerted, or the bed is composed of loose sediment which can be mobilized by such stresses, then the bed will be lowered purely by clearwater flow. However, if the river carries significant quantities of sediment, this material can act as tools to enhance wear of the bed (abrasion or scraping). At the same time the fragments themselves are ground down, becoming smaller and more rounded (attrition).

River Processes that move materialsthebritishgeographer.weebly.com

ErosionErosion is the breaking down of material by an agent. In the case of a river, the agent is water. The water can erode the river’s channel and the river’s load. A river’s load is bits of eroded material, generally rocks, that the river transports until it deposits its load.A river’s channel is eroded laterally (side to side) and vertically (up and down) making the channel wider and deeper. The intensity of lateral and vertical erosion is dictated by the stage in the river’s course.

Erosion and Deposition in Rivers www.Indiana.eduhttps://geographyas.info/rivers/river-processes/www,xtlearn.net

Wind can also move rocksRocks and rock particles are carried by the flow of air much as they are carried by the flow of water.

http://legacy.belmont.sd62.bc.ca/teacher/geology12/photos/erosion-water/saltation.jpg

Mojave Desert Sand

Sand blowing on the Kelso Dunes, California. Sediments can blow from the land. Some of it lands in the rivers.

Photograph taken by Mark A. Wilson (Department of Geology, The College of Wooster). Released into the public domain (by the author).

Dust blows from the Sahara Desert over the Atlantic Ocean towards the Canary IslandsDust and Smoke off the West Coast of Africa Dust and smoke mixed over the Atlantic as the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite took this picture on July 28, 2007. In this image, a beige dust plume hundreds of kilometers long blows off the west coast of Africa in a clockwise direction, toward the northwest. West of that plume is another, lighter plume, which may consist of dust or some combination of dust and smoke. As the dust blows off the Sahara, a plume of pale gray smoke blows off Gran Canaria [due to an important forest fire], also curving toward the northwest. While the smoke largely skirts Tenerife, it heads straight for San Sebastián [La Gomera island] and Santa Cruz [La Palma island].NASA GSFC - MODIS Rapid Response Team at NASA GSFC

By NASA GSFC - MODIS Rapid Response Team at NASA GSFC, Public Domain, https://commons.wikimedia.org/w/index.php?curid=2506991

Channel Processes

Gravity causes the heavier particles of the stream load to fall out earlier. The smaller and lighter particles are carried longer distances. www.acegeography.com

Stream LoadA schematic diagram of where the different types of sediment load are carried in the flow. Dissolved load is not sediment: it is composed of disassociated ions moving along with the flow. It may, however, constitute a significant proportion (often several percent, but occasionally greater than half) of the total amount of material being transported by the stream.

PSUEnviroDan - Own work Creative CommonsStream cross section showing stream load•File:Stream Load.gif•Created: 2 April 2008

Rivers break down rocks.

Attrition smooths the edges of broken rock, and sediment becomes smaller.

www.coolgeography.co.uk

Abrasion by waterConstant abrasion by rapidly moving water wears down these boulders. Over time, the sharp edges are worn away, leaving smooth round stones.

http://www.panoramio.com/photo/32774017

Rocky River Bed

http://www.primaryhomeworkhelp.co.uk/rivers/glossary.htmlhttp://demo.fabthemes.com/endolf/rocky-river-bed/

Dry River Bed

Dry river bed Dublin Indian Run Falls OH USADuring a long period with no rain, some shallow rivers will have a dry period. When rain returns, the river will flow again.

https://images.search.yahoo.com/yhs/search;_ylt=A0LEV79NcN5XhxwAH70nnIlQ?p=river+bed&fr=yhs-mozilla-04&fr2=pivweb&hspart=mozilla&hsimp=yhs-004#id=5&iurl=http%3A%2F%2Fstatic.panoramio.com%2Fphotos%2Flarge%2F40084864.jpg&action=click

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Fluvial Landforms: Alluvial Fans

Stream bed load deposited in the form of a low cone issuing from the canyon mouth.

Adjoining alluvial fans form a continuous deposit called an alluvial apron or a bajada. This view is of a bajada in Death Valley. Image Courtesy United States Geological Survey; Image source: Earth Science World Image Bank http://www.earthscienceworld.org/images Credit Line: Copyright © Michael Collier

Fluvial Landforms: DeltasDeposition of material at the river's mouth. Upon reaching a quiet body of water, the velocity of the water in the river slows greatly and the water is unable to carry its load of sediment. Deposition occurs and produces a feature we know as a delta. It is named after the Greek letter delta (looks like an upside-down triangle). Example: Nile River Delta (below). Multiple channels are seen flowing away from the main channel and these are called distributaries (not visible in this image)

This image of the northern portion of the Nile River. Image Courtesy United States Geological Survey; Image source: Earth Science World Image Bank http://www.earthscienceworld.org/images Courtesy NASA, Visible Earth

Braided Streams

Toklat River, East Fork, Polychrome overlook, Denali National Park, Alaska. – "The river here was a wide bed of gravel with several channels where the water flows. Sometimes the water switches between channels.“Dawn Endico, Menlo Park, California - flickr.com

Downcutting

Stream erosion in which the cutting is directed in a downward direction.

McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

http://legacy.belmont.sd62.bc.ca/teacher/geology12/photos/erosion-water/downcutting1.jpg

Fluvial Landforms: Slot CanyonsSteep sided, often narrow canyons carved into rock by rivers. Often form in areas of frequent flash flooding and hikers caught in flash floods in these canyons can be in great danger.

Example of a slot canyon in Utah. Slot canyons are very narrow canyons and some are so deep and narrow that the canyon bottom can be in near-total darkness even at mid-day.

Image Courtesy United States Geological Survey; Image source: Earth Science World Image Bank http://www.earthscienceworld.org/images Credit Line: Copyright © Thomas McGuire

V-Shaped Valleys

A pothole that has formed along the River Clyde.Copyright Jim Ness. Licensed under the Creative Commons 2.0 license.

Abrasion and erosionWind (photo on the right) and water (below) can reshape stones as they carry small bits of sand to rub (abrasion) the surface away and carry it along (erosion).

• Desert sands sculpted this rock into a shape called a HOODOO.

• http://legacy.belmont.sd62.bc.ca/teacher/geology12/photos/erosion-water/hoodoo.jpg• http://legacy.belmont.sd62.bc.ca/teacher/geology12/photos/erosion-water/abrasion.jpg

V-shaped valleyA V-shaped valley forms through a geological process called erosional down-cutting in which a strong and fast moving river or stream erodes or cuts a path through rock. A V-shaped valley may also be referred to as a river valley. The main characteristics of this valley type is that it is narrow with steep and sloped sidesThe Grand Canyon is an example of a V-shaped valley, which was formed during millions of years as the Colorado River cut a path through the Colorado Plateau. The Grand Canyon is 277 miles in length and approximately more than 1 mile in depth.

http://legacy.belmont.sd62.bc.ca/teacher/geology12/photos/erosion-water/v-shaped%20valley%202.jpgPhoto from Creative Commons